This project is to define the tumor-bearing state in terms of responses of lymphoid cells to antigenic components of soluble tumor membranes, and thereby to examine the immunobiology of the tumor-host relationship. Both mouse and human model tumors are being employed. Current efforts are directed at characterizing the membrane antigens involved, the cellular subsets responding, and interactions between tumor antigen, antibody, and all functions including proliferation or cytotoxicity. BIBLIOGRAPHIC REFERENCES: Dyminski, J. W., and R. T. Smith; Nature of the B cell helper activity in mixed lymphocyte reactions between immunocompetent mouse thymus cells. Fed. Proc. 35 #3, 1976, abstract. Gainor, B. J., Forbes, J. T., Enneking, W. F., and Smith, R. T.; A method of immunologic assay in human osteosarcoma. Clin. Ortho. 3:83 (Sept. 1975).